The present invention relates to a driving mechanism for the control of the needle-bar and tube-bars in fast knitting machines, of the type comprising: a support bed provided with at least two side posts; at least one drive shaft rotatably engaged through each of said posts; a pair of swinging arms each rotatably connected to one of said posts and fixedly engaging a needle-bar; a pair of first driving connecting rods each of them exhibiting one end pivoted to one of said swinging arms and the opposite end operatively engaged on one eccentric carried by said first drive shaft; a second drive shaft rotatably engaged to each of said posts; a pair of oscillating supports each of them being slidably engaged in a substantially vertical direction with one of said posts and engaging at least a tube-bar at one end thereof; a pair of second driving connecting rods each exhibiting one end connected to one of said oscillating supports and the opposite end operatively engaged with a second eccentric carried by the second drive shaft; said first and second drive shafts being driven simultaneously in rotation in order to respectively cause the operation of the needle-bar according to a substantially horizontal oscillatory movement and the operation of the tube-bar according to a substantially vertical oscillatory movement.
It is known that in fast knitting machines the needle-bar is fastened by its opposite ends to two swinging arms which are pivoted, according to a horizontal axis, to two posts forming part of the machine bed. Acting upon each of said swinging arms is one driving connecting rod operatively engaging with a respective eccentric mounted to a main shaft the opposite ends of which are rotatably engaged through said posts. The main shaft is driven in rotation by a motor in order to impart an oscillatory movement in a substantially horizontal direction to the needle-bar, through the eccentrics, first driving connecting bars and swinging arms.
The rotation of the main shaft is transmitted, by a pair of toothed belts or the like acting on the opposite ends of the main shaft, to a pair of second shafts each of which is rotatably engaged to one of the posts. Associated with each of said second shafts is a second eccentric operatively engaging a second driving connecting rod. The second driving connecting rods give rise to the movement of two oscillating supports each of which is slidably engaged with two guide rods upstanding from the corresponding post.
Engaged with the oscillating supports by its opposite ends is at least a tube-bar carrying a number of threading tubes arranged such as to cooperate with the needles carried by the needle-bar and with other instrumetalities of the knitting machine in order to carry out the knitting of the workpiece.
Due to the rotation transmitted to the second drive shafts, the second connecting rods actuates the supports, and hence the tube-bar or bars transmitting a substantially vertical oscillatory movement to the same.
Also operating on the tube-bars is a second driving mechanism which, actuated by a so-called "glider chain" transmits an oscillatory movement in a horizontal direction to the bars themselves, which movement is vectorially combined with the vertical oscillations transmitted by the above described driving mechanism. It is to be noted that one of the most important problems connected with fast knitting machines resides in the strong vibrations to which said machines are submitted when they are actuated at high speed. Obviously due to the presence of these vibrations it is impossible to increase the work speed beyond given values, which brings about a limitation in the productivity of these machines. In addition, due to said vibrations the different parts of the machine are submitted to high mechanical stresses and it is therefore necessary to provide the machine with heavy beds and frameworks in order to ensure a sufficient steadiness to the same.
Most of the above vibrations have been found to be caused by the reciprocating horizontal movement of the needle-bar and the reciprocating vertical movement of the tube-bars. In fact, each of said bars as well as the different elements connected thereto, form an important mass which is submitted to high decelerations and accelerations each time, a reversal of movement occurs. As a result of said accelerations and decelerations there are high forces of inertia which are directly transmitted to the machine framework.